A student starts from the origin and walks 2km east in 0.5h, then 3km west in another 0.5h, and finally 1km east in 0.25h. Which statement about his motion for the entire 1.25h interval is correct?
(a) Average speed=4.8km h−1;average velocity=4.8km h−1 east.
(b) Average speed=4.8km h−1;average velocity=0.8km h−1 west.
(c) Average speed=4.8km h−1;average velocity=0km h−1.
(d) Average speed≈4.7km h−1;average velocity=0km h−1.